A numerical study of thermal ignition

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:7267983

Lutz, A E

First, chemical kinetics computations are used to quantify the influence of disturbances on the induction times for homogeneous mixtures at constant volume. The constant-volume approximation is then replaced by a gas dynamic constraint to model ignition of an exothermic center. Finally, a one-dimensional model for an inert gas with energy deposition is developed to simulate the gas dynamics of the explosion. Constant-volume computations are used to identify initial conditions under which a mixture is highly temperature sensitive. The reduction in the induction time caused by a disturbance of known amplitude is determined by imposing a volume oscillation of the mixture. Although the hydrocarbon fuels are less sensitive than hydrogen, all fuels respond to disturbances under some conditions. The exothermic center model of a hot spot considers a small, homogeneous kernel of reactive mixture surrounded by an inert mixture. The local ignition resembles a constant-pressure process, except that a pressure pulse occurs in the kernel, generating a weak shock wave in the surrounding mixture. The one-dimensional gas dynamics model uses a nonlinear finite difference scheme for the convective fluxes and a fully-implicit adaptive mesh scheme to capture and resolve sharp fronts. Simulations of a kernel explosion show that although the shock wave is weak, it causes a significant temperature disturbance in the mixture many diameters away from the kernel.

• Research Organization: California Univ., Davis, CA (USA)
• OSTI ID: 7267983
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400800* -- Combustion
Pyrolysis
& High-Temperature Chemistry
CHEMICAL REACTION KINETICS
COMBUSTION KINETICS
DISPERSIONS
ELEMENTS
EXPLOSIONS
FINITE DIFFERENCE METHOD
FUELS
GAS FUELS
HYDROCARBONS
HYDROGEN
IGNITION
ITERATIVE METHODS
KINETICS
MATHEMATICAL MODELS
MIXTURES
NONMETALS
NUMERICAL SOLUTION
ONE-DIMENSIONAL CALCULATIONS
ORGANIC COMPOUNDS
REACTION KINETICS
SHOCK WAVES
TEMPERATURE DEPENDENCE
TEMPERATURE GRADIENTS
TIME DEPENDENCE